1. Field of the Invention
This invention relates to feed control for a brush chipper. More particularly, the invention relates to a method and apparatus for providing a lower feed stop bar that reduces nuisance trips.
2. Background Art
Control aspects of brush chippers are provided for control and safety of machinery and operators. One control aspect, a lower feed stop bar, is located at an infeed side of an infeed table or shelf on the brush chipper. It is situated such that an operator may stop the feed of brush for any reason by pushing the lower feed stop bar toward the brush chipper. Present day feed stop bars are typically pivoted from pivot arms at each end of a control bar. The control bar extends across the infeed end of the infeed table. In the known art, the pivot arms extend upward from the control bar and the axis of rotation is above and toward the outfeed end of the brush chipper more than the control bar.
The force of gravity, aggravated by machine vibrations, tends to force the lower feed stop bar toward its forward position, thereby causing nuisance trips.
The infeed table of a brush chipper is subjected to significant vertical accelerations that occur when loading branches/logs onto the feed table. When a log is dropped onto the table it moves downward, stops and then moves upward. As the downward movement starts the feed table and the feed stop bar are subjected to a negative acceleration, wherein the feed stop bar will tend to rotate clockwise if the pivot axis is to the left of the mass of the feed stop bar as shown in FIGS. 1 and 2 of U.S. patent application Ser. No. 2004/0108397, for example, and would tend to rotate counter-clockwise if the pivot axis was to the right of the mass of the feed stop bar. As the feed table is moving downward, the tires and suspension of the machine are being compressed, and eventually the movement changes direction, and energy stored in the tires and suspension cause the machine to move upwards. During this upward movement, when the direction is reversed, the feed stop bar is subject to acceleration in an opposite direction. Having the design of the feed stop bar, including the position of the pivot axis to the left of the mass of the stop bar, as shown in FIGS. 1 and 2 of No. U.S. patent application Ser. No. 2004/0108397, has been observed to result in false trips due to the dynamic loading, the acceleration of the feed table previously described.
U.S. Pat. No. 5,692,548 by Bouwers et al. and U.S. Pat. No. 5,692,549 by Eggers are hereby incorporated by reference and disclose brush chippers having many components of the brush chippers on which the present invention is used. Some of the pertinent components are: a material inlet, or feed table assembly, a plurality of feed rollers, and a chipping drum. The feed rollers are driven by hydraulic motors.
There is, therefore, a need for a method and apparatus for a lower feed stop bar pivoted and oriented in a fashion to reduce the possibility of nuisance trips while providing all the functionality of lower feed stop bars in the prior art.